seconds to time, including days and weeks , only show biggest part

function timeConvert(num) {
  days = Math.floor(num / 86400);
  num -= days * 86400;
  hours = Math.floor(num / 3600) % 24;
  num -= hours * 3600;
  minutes = Math.floor(num / 60) % 60;
  num -= minutes * 60;
  seconds = num % 60; 
  let result = days + ":" + hours + ":" + minutes + ":" + seconds;
  return result;
}

timeConvert(3601);